1. Field of the Invention
The present invention relates to a fluid-mechanical device, especially for a fan device for high torque output.
2. Description of Related Art
A fan device is applied for intercepting fluids of wind or liquid, and to generate torque to drive a generator. With reference to FIG. 7, FIG. 8 and FIG. 9, a conventional fan device has two base plates 70, a spindle 80, and multiple fans 90. The base plates 70 are arranged parallel. The spindle 80 is mounted on a middle position on a side of the base plate 70. The fans 90 are circularly mounted between the base plates 70. Each fan 90 has an outer side 91, an inner side 92, and a driven portion 93. The outer side 91 and the inner side 92 are formed on the fan 91 respectively, and the inner side 92 is nearer the spindle 80 than the outer side 91. The driven portion 93 is formed between the outer side 91 and the inner side 92. When the middle position of the driven portion 93, the inner side 92, and the outer side 91 are located at the same horizontal plane and at equal distance from one of the base plates 70, the connecting line that connects the middle position of the driven portion 93 and the spindle 80 is located within the area defined between the connecting line that connects the outer side 91 and the spindle 80 and the connecting line that connects the inner side 92 and the spindle 80.
When the fluid flows across the fans 90, the fluid drives the driven portion 93 to provide a torque for the fans 90 to rotate the base plates 70. When the base plates 70 are driven to rotate, the spindle 80 is also driven to rotate by the base plate 70 that is mounted with the spindle 80. A generator C is connected with the spindle 80 and is provided with the torque by the spindle 80. However, the connecting line that connects the driven portion 93 and the spindle 80 is located within the area between the connecting line that connects the outer end 91 and the spindle 80 and the connecting line that connects the inner end 92 and the spindle 80, so the frontal area of each fan 90 pushed by the fluid is small. Therefore, the speed of the fans 90 is slow, and the torque outputted from the fan device is low.